Desulfurizing hydrocarbons with lead oxide-clay mixtures



w/ kopz/cf DESULFURIZING HYDROCARBONS WITH LEAD OXIDE-CLAY MIXTURES June13, 1961 r/e54 77/V6 P4 1? 77A LL Y EXHA 4157-50 550 PAaD uc 7' FRESHFEED INVENTOR. V/A/CEA/T KENNY BY United Patented June 13, 19612,988,499 DESULFURIZING HYDROCARBONS WITH LEAD OXIDE-CLAY MIXTURESVincent Kenny, Whittier, Calif., assignor to Union Oil Company ofCalifornia, Los Angeles, Calif., a corporation of California Filed May12, 1958, Ser. No. 734,679 17 Claims. (Cl. 208-197) This inventionrelates to the sweetening of mercaptancontaminated hydrocarbons, andespecially light hydrocarbons such as propane, butane, pentane and lightnaphtha fractions. The new process utilizes as the sweetening agent, abed of dry, or substantially dry, lead oxide (litharge) mixed with anadsorbent clay such as fullers earth. The contacting is carried out insuch manner, more particularly described hereinafter, as to counteractthe normal tendency of the clay-lead oxide treating agent to increasethe corrosivity of the feed. In a preferred modification, the feed maybe sweetened and simultaneously rendered non-corrosive. I

It is an object of this invention to provide an inexpensive sweeteningprocess based on ambient temperature, solid-liquid contactingtechniques. Another object is to provide methods for utilizing clay-leadoxide mixtures for sweetening without increasing the corrosivity of thefeed. A more specific object is to obtain both sweetening andelimination of corrosive sulfur in a single contacting process. Otherobjects will become apparent from the following more detaileddescription.

It is known that mercaptans will react with certain lead compounds togive lead mercaptides. The wellknown doctor sweetening process is basedupon the reaction of aqueous sodium plumbite with sour hydrocarbons toform lead mercaptides, followed by oxidation of the lead mercaptideswith free sulfur to give lead sulfide and the more innocuous alkyldisulfides. However, the standard doctor sweetening process isdisadvantageous in that it requires the use of large volumes ofexpensive reagents, careful control of quantities, and a plurality oftreating stages, all of which render the process expensive.

In attempting to carry out a simpler sweetening process by contactingsour hydrocarbons with dry lead oxideclay mixtures, I have found thatsweetening may be obtained, but for unknown reasons the resultingproduct is much more corrosive than the original feed. In some cases aninitially non-corrosive feed is rendered highly corrosive by thetreatment. Corrosiveness is defined in analytical terms herein as thetendency of a hydrocarbon fraction to discolor a copper strip by theformation of copper sulfide thereon under standard conditions.Corrosiveness is in some cases more undesirable than mercaptan sulfur,since it commonly results in corrosion of storage tanks, pipelines, andvalves, and also leads to the formation of undesirable deposits ininternal combustion engines. Mercaptan sulfur is ordinarilynon-corrosive; corrosive sulfur is thought to comprise for the mostpart, dissolved free sulfur, hydrogen sulfide, and/or carbonyl sulfide.

In further exploring the clay-lead oxide sweetening process, I haveunexpectedly found that when the contacting with sour hydrocarbon iscontinued for a suflicient length of time, the corrosivity of theproduct decreases and eventually vanishes. Thus, whereas the initialproduct is sweet but highly corrosive, the product recovered afterseveral hours of contacting is not only sweet, but non-corrosive to thecopper strip test. Presumably some unknown material is present in thefresh bed which either itself contributes corrosive sulfur, or convertsnon-corrosive sulfur in the feed to corrosive sulfur. In any event,after a few hours on-stream, this material is apparently destroyed orneutralized before the treating capacity of the bed has been exhausted.After this point is reached, a feed which is initially sour andcorrosive may be rendered both sweet and non-corrosive.

To give best elfect to this discovery, I have devised a dual-bedtreating process which permits continuous uninterrupted operation, togive a continuously sweet and non-corrosive product, while at the sametime permitting periodic renewal of exhausted treating beds. Thisprocess may be best understood with reference to FIGURE 1 of theaccompanying drawing which illustrates one suitable form of apparatus.

The principal units of apparatus comprise two identical cylindricalreactors 1 and 2 which may be constructed of mild steel, stainlesssteel, or other suitable structural materials. Each unit comprises acylindrical shell 3, and upper and lower cup-shaped closure members 4and 5. The closure members 4 and 5 are removably attached to cylindricalshell 3 by means of annular flanges 6, which are secured together inconventional manner by means of bolts or other suitable means. Eachreactor is also equipped with an upper liquid inlet port 7 and productoutlet port 8. The appropriate fluid transfer lines, as well as thenecessary flow-regulating valves, are indicated schematically and theiroperation 'will be described more in detail in connection with theoperation of the process.

To illustrate the operation of the process from an initial start-up,each reactor, 1 and 2, is charged with fresh treating beds as follows:First a shallow layer 10 of gravel or other coarse aggregate is placedin the lower section of the reactors, resting upon a perforatedsupporting plate 11. On top of gravel layer 10, a layer'of finerfiltering material '12 is deposited to prevent the washing out of leadoxide. Filter layer 12 may consist for example of glass wool, asbestosor other equivalent. The active treating bed 13 is then packed in abovefilter bed 12, and extends almost to the top of the reactor. Finally,another layer of gravel or aggregate 14 may be placed on top of thetreating bed.

With both reactors charged with fresh treating beds, it is next desiredto pass the feed through one reactor until that reactor is exhausted ofits corrosion-additive propensities. To accomplish this a firstcontact-ing sequence is established as follows:

Contacting sequence 1.Valves 15 and 19 are opened and valves 16, 17, 18and 25 are closed. The feed then flows in through line 20, valve 15,reactor inlet 7, reactor 1, reactor outlet 8, valve 19 and productoutlet line 22. This sequence is continued until tests indicate that theproduct is non-corrosive to the copper strip test. The initiallyobtained corrosive product may be recycled to feed storage not sho'wn,and again treated to remove its corrosiveness subsequently in theprocess.

When the product from reactor 1 becomes non-corrosive, it has been foundthat passing it through reactor 2, which contains a virgin bed oftreating material, will again render it corrosive. It is hence necessaryto condition the bed in reactor 2 so as to eliminate itscorrosionadditive function. To accomplish this, a second contactingsequence is initiated as follows:

Contacting sequence 2.Valves 15, 18, 25 and 26 are closed, and valves16, 27, 17 and 19 are opened, whereby the feed flows through line 20,valve 16, reactor 2, line 29, valve 27, line 30, valve 17, reactor 1,valve 19, and product outlet line 22. During the initial phases of thistreating sequence, the product in line 30 is periodically reactor 1removes the corro'sivity imparted in reactor 2,

and the final product is both sweet and non-corrosive. At this point thestart-up operations are complete and continuous production of sweet,non-corrosive product may be indefinitely maintained.

. Contacting sequence 2 is continued until the product sampled from line32 becomes sour to the doctor test. When this occurs, it is anindication that the bed in reactor 2 is exhausted. If it is desired tomaintain continuous, uninterrupted operation, a third contactingsequence is initiated as follows:

Contacting sequence 3 (0pti0nal).Valves 16, 17, 18 and 25 are closed,and valves 15 and 19 are opened, whereby the feed flow is exclusivelythrough reactor 1, while the product in line 22 continues sweet andnon-corrosive. While this flow is being maintained, the closure members4 and 5 of reactor 2 are removed, the spent bed is discharged, and afresh bed of lead oxide and clay is added. It is preferable toaccomplish the renewal of the bed in reactor 2 before reactor 1 isexhausted, in order that sufficient treating capacity in reactor 1 willremain to effect a clean-up of the initial corrosion to be added by thenew bed in reactor 2 when it is placed on-stream. If continuousoperation is not necessary, reactor 1 may of course be simply shut downwhile reactor 2 is recharged. In this event, the fourth contactingsequence immediately follows the second.

Contacting sequence 4.-To initiate the new bed in reactor 2, valves 15,26, 25 and 18 are closed, and valves 16, 27, 17 and 19 are opened,whereby the product flows first through reactor 2 then through reactor1, and into line 22. This operation is co'ntinued until the efiiuentfrom reactor 2, which may be removed for sampling through line 32,becomes non-corrosive. At this point, or shortly thereafter, it ispreferable to switch the feed flow so that it will contact the bed inreactor 1 ahead of the bed in reactor 2, rather than to complete theutilization of the relatively new bed in reactor 2. This provides forsmooth, continuous operation, which otherwise might not be obtained ifreactor 1 is used merely for stand-by, and/or clean-up treatment. Insuch an event reactor 2 would be continually recharged, and the eventualexhaustion of reactor 1 might upset the cycle of operations. Hence,after the initial upstream treatment of a new bed, it is preferable toplace it downstream so that the oldest bed will be next exhausted. Thischangeover i effected by initiating a fifth treating sequence.

Contacting sequence 5.Valves 17, 16, 19 and 27 are closed, and valves15, 18, 26 and 25 are opened, whereby feed flows first through reactor1, then line 30, then reactor 2, and into line 22 via valve 25. Thisflow sequence is maintained until the product sampled through line 32becomes sour, indicating exhaustion of the bed in reactor 1. At thispoint, if continuous operation is desired, cycle 6 is initiated.

Contacting sequence 6 (optional).-Valves 15, 26, 27 and 19 are closedand valves 16 and 25 are opened, whereby the feed flows exclusivelythrough reactor 2, and the product in line 22 continues sweet andnon-corrosive while the bed in reactor 1 is being renewed. To conditionthe new bed in reactor 1, a seventh contacting sequence is initiated.

Contacting sequence 7.Valves 17, 16, 19 and 27 are closed, and valves15, 18, 26 and 25 are opened, whereby the feed flows through reactor 1,line 30, reactor 2, and into product line 22, and continues sweet andnoncorrosive. This flow sequence continues until the product sampledthrough line 32 becomes non-corrosive. At this point, a complete cycleof regeneration and conditioning has been accomplished, and the valvesare hence adjusted for passage first through reactor 2 and then reactorI as in sequence 2 above. This cycle of operations may be continuedindefinitely without interruption of product flow to obtain acontinuously sweet and non-corrdsive product.

The above description is not intended to be limiting in scope; obviouslymany variations may be made without departing from the scope of theinvention.

One such variation, which is advantageous from the standpoint of initialcost and simplicity of operation (especially in small operations),consists in using a single treating unit, and when such unit becomesexhausted, renewing or regenerating only the major upstream portion ofthe bed, and leaving downstreamwardly, near the product outlet, a minorportion of the old bed. This mode of operation is illustrated in FIGURE2, and is most advantageous where the feed contains not more than about0.5 gram-atom of corrosive sulfur for each gram-atom of mercaptansulfur.

To initiate such an operation, the treating unit 40 may be charged witha fresh bed of clay-lead oxide, and the initially corrosive efiluenttherefrom recycled to feed storage at 42, via lines 44 and 46 for latertreatment to remove the corrosive sulfur. As soon as the effiuentbecomes noncorrosive (and sweet), product is collected from lines 44 and48 until tests indicate a break-through of mercaptan sulfur. At thispoint, the downstream portion of the bed is still capable of removingcorrosive sulfur, but will not remove mercaptan sulfur.

To regenerate the exhausted bed, it is desirable to replace the majorupstream portion thereof with fresh material 50, but to maintain a minorportion 52 of the old bed in place at the effluent end of the reactor.The proportion of the old bed to be retained may vary from about 1% orless, to about 20% of the total. Ordinarily, no more of the old bed isretained than is required to absorb the corrosive sulfur contained inthe initial portions of feed traversing the fresh portion of the bed.This amount may vary depending upon specific characteristics of feed,lead oxide charge and the type of clay used.

As an example of this operation, a stream of liquid butane-pentanecontaining 30 parts per million of mercaptan sulfur and 6 parts permillion of elemental sulfur is passed downwardly through a fresh bed of75% fullers earth-25% lead oxide (litharge) at a liquid hourly spacevelocity of about 2. The initial sweet product is found to be morecorrosive than the feed, and is hence recycled to the feed storage.After about 18 hours, the corrosion number of the efiluent drops tozero, and a sweet and noncorrosive product is then collected for about60 days. after which the product begins to test sour to the doctor test.

The fiow of feed is then terminated and the entire bed is dumped. About10% thereof, preferably selected mainly from the midsection of the oldbed (e.g. the section located above the lower 10% and below the top 10%)is dumped back into the bottom of the reactor. The upper portion is thenrefilled with fresh claylead oxide mixture. The regenerated bed is thencapable of producing sweet noncorrosive product for about 55 days fromthe outset.

In this manner, the regenerations may be continued indefinitely withoutdanger of building up totally exhausted clay-lead oxide mixture (i.e.mixture which is exhausted of both mercaptan-removing and corrosive sulfur-removing capacity) at the bottom of the bed. Thus, a continuouslysweet and noncorrosive product is obtained.

The treating beds employed herein preferably consist of mixtures ofcommercial litharge (PhD), and any suitable adsorbent clay. Suitableclays include for example fullers earth, bauxite, bentonite and thelike. Preferably. the clay should have a slightly alkaline reaction,though this does not appear to be essential. The preferred material isAttapulgus clay, which is a slightly alkaline fullers earth consistingessentially of hydrous magnesiumaluminum silicate. Other materials suchas diatomaceous earth may be employed. The clay is preferably employedin weight-excess of the lead oxide, but any proportions which provide asuitably porous bed may be utilized. Preferably, the clay shouldcomprise between about 40% and 90% by weight of the bed, the remainderbeing lead oxide, and the two components should be intimately admixed bysuitable agitation.

The reaction in the treating beds is quite rapid at ordinary atmospherictemperatures, and hence space velocities may range between about 0.5 and50 liquid volumes per volume of bed per hour, and preferably betweenabout 1 and 20 volumes. The sweetening reactions are substantially morerapid in the case of lower-boiling hydrocarbons, and hence elevatedtemperatures may be employed when treating higher-boiling materials suchas gasoline or kerosene. For low-boiling materials, e.g. propane orlight naphthas, preferred temperatures may range between about 50 and150 F.; for heavier materials up to kerosene, temperatures of about 100to 200 F. may be preferred.

As indicated, substantially any hydrocarbon feed may be treated herein.The process appears best adapted for the treatment of light hydrocarbonssuch as propane, butane, pentane, hexane and the like, as well as lightgasolines. The high-boiling feeds such as kerosene, especially thosecontaining aromatic hydrocarbons, may tend to dissolve lead mercaptidesfrom the treating bed, and hence suitable precautions must be observedin treating such stocks. Preferably, the feed is treated in liquidphase, but vapor phase operations are also contemplated. Preferably, thefeed should contain, or be adjusted to contain, not more than about 0.5gram atom of corrosive sulfur for each gram atom of mercaptan sulfur.The usual feeds will be found to contain between about 2-20 p.p.m. ofelemental sulfur, and about 5-100 p.p.m. of mercaptan sulfur.

When any of the treating beds described herein become totally exhaustedit is in most cases economically feasible to discard the exhausted bedand replace it with a new one. However, where considerations of cost areimportant, the exhausted beds may be regenerated by stripping out theadsorbed hydrocarbons, drying, and oxidizing the bed with air or oxygenat temperatures between about 600 and 1500 F. for several hours. Theexhausted beds comprise mainly lead mercaptides with perhaps some leadsulfides, depending upon the nature of the feedstock, and especially theratio of mercaptan sulfur to corrosive sulfur in the feed.

The doctor test employed herein is well-known, and involves shaking asample of the hydrocarbon with aqueous sodium plumbite, followed by theaddition of a pinch of elemental sulfur to the hydrocarbon phase. Aresulting dark color is a positive reaction indicating a sour product,whereas if no coloration develops the product is sweet, i.e. containsless than about 3-4 p.p.m. of mercaptan sulfur.

The copper strip corrosion test employed herein is a standard A.P.I.method, which involves heating a 40 ml. sample of the feed with a /2" x3" strip of clean, polished copper for 3 hours at 50 C. The strip isthen removed and compared with a fresh strip. The degree of corrosivityis indicated on the following scale:

The following examples will serve to illustrate some of the criticalfeatures of the process, but are not intended to be limiting in scope.

Example I A dual-unit treating plant similar to that illustrated in thedrawing was constructed comprising two treating beds, each made up of600 pounds of 15-30 mesh Attapulgus 6 fullers earth, and 200 pounds ofcommercial litharge intimately admixed with each other.

It was found that when a liquid propane stream containing 10 parts permillion of mercaptan sulfur and 5 parts per million of elemental sulfurwas contacted in one of the reactors at atmospheric temperatures, theproduct after one hour of treatment was doctor sweet, but gave a copperstrip corrosion number of 5, whereas the initial feed showed a copperstrip corrosion number of only 1. After the contacting had beencontinued for 24 hours at 750 barrels per day, it was observed that theproduct was still doctor sweet, but the corrosion number had diminishedto zero, indicating no corrosive sulfur.

The flow of feed was then adjusted to pass first through the virgin bedin the second reactor, and then through the partially exhausted bed. Theinitial product from the virgin bed was again observed to be highlycorrosive, while the final product from the second, partially exhaustedbed was found to be doctor sweet and had a corrosion number of zero.This clearly illustrates the ability of a partially exhausted bed toeliminate corrosive materials resulting from treatment in a fresh bed.

Example II A stream of liquid pentane containing 40 parts per million ofmercaptan sulfur and 5 parts per million of elemental sulfur wascontacted with a fresh 75% fullers earth-25% lead oxide bed atatmospheric temperature, and at a liquid hourly space velocity of about1.9. The initial product was sweet, but had a copper strip corrosionnumber of about 4, whereas the feed had a corrosion number of 1. Theproduct continued to test highly corrosive for several hours. Afteroperating for 24 hours, the corrosion number of the product dropped tozero, and the product was still sweet to the doctor test. This treatmentwas then continuously employed for 65 days, at which point the productbecame sour to the doctor test, indicating exhaustion of the bed.

Example III A blend of light California straight-run and thermallycracked naphthas boiling between about 200 and 350 F. and containing 50parts per million of mercaptan sulfur, and having a copper stripcorrosion number of 4 was treated in a fresh bed as described in ExampleII, and the product after 8 hours was found to be doctor sweet but had acorrosion number of about 5. Continued treatment for another 24 hoursgave at the conclusion thereof, a product of corrosion number zero andnegative doctor test.

This application is a continuation-in-part of my prior applicationSerial Number 614,518, filed October 8, 1956, now abandoned.

The foregoing disclosure of this invention is not to be considered aslimiting since may variations may be made by those skilled in the artwithout departing from the spirit or scope of the following claims.

I claim:

1. In a process for removing corrosive sulfur and mercaptan sulfur froma hydrocarbon feed containing the same, wherein said feed is treated ina contacting column with a bed of clay-lead oxide mixture, the improvedmethod of operating said process to obtain a regenerative operationproducing a continuously sweet and noncorrosive product, which comprises(1) first passing said feed through a fresh bed of clay-lead oxidemixture until the mercaptan-removing capacity of said bed issubstantially exhausted and then terminating the passage of feedtherethrough before the corrosive sulfur-removing capacity of said bedhas been exhausted, (2) removing from the contacting column at least theupstreamward major portion of said exhausted bed, (3) refilling theupstreamward major portion of said contacting column with freshclay-lead oxide mixture while retaining at the downstream extremitythereof a minor portion of said exhausted bed, (4) then resuming thepassage of feed through the regenerated bed to obtain a sweet andnoncorrosive product.

2. A process as defined in claim 1 wherein said claylead oxide mixtureis composed of a major proportion of alkaline fullers earth, and a minorproportion of commercial litharge.

3. A process as defined in claim 1 wherein said hydrocarbon feedcontains at least two gram-atoms of mercaptan sulfur per gram-atom ofcorrosive sulfur.

4. A process as defined in claim 1 wherein the retained minor portion ofsaid exhausted bed is selected mainly from the 80% midsection of saidexhausted bed.

5. A method for regenerating a clay-lead oxide treating bed which hasbeen previously exhausted of its mercaptan-removing capacity by contactwith a sulfur-containing hydrocarbon feed but is not yet exhausted ofits corrosive sulfur-removing capacity, which comprises replacing theupstrearnwardly-located major portion of said exhausted bed with freshclay-lead oxide mixture, and retaining a minor portion of said exhaustedbed'at the downstream extremity.

6. A process as defined in claim 5 wherein the retained minor portion ofsaid exhausted bed comprises about 1-20% thereof, and wherein saidretained minor portion is selected mainly from the 80% mid-section ofsaid exhausted bed.

7. A process as defined in claim 5 wherein said claylead oxide mixtureis composed of a major proportion of alkaline fullers earth, and a minorproportion of commercial litharge.

8. A process for sweetening a sour corrosive hydrocarbon feedstock toobtain a sweetened product of reduced corrosivity, which comprisesproviding two beds A and B of solid lead oxide-clay mixture, bed A beingvirgin and bed 8 being partially exhausted as a result of previouscontacting with feedstock for a period of time such that the initiallycorrosive eiiiuent therefrom has become non-corrosive but is stillsweet, establishing a first contacting sequence wherein said feed ispassed first through bed A and then through bed B, continuing said firstcontacting sequence until the initially corrosive effiuent from bed Abecomes non-corrosive and bed A is partially exhausted as above defined,then establishing a second contacting sequence wherein said feed ispassed first through bed B and then through bed A, continuing saidsecond contacting sequence until the initially sweet effiulent from bedB becomes sour and bed B is exhausted, then replacing bed B with a newbed C of lead oxideclay mixture, and reestablishing said firstcontacting sequence with the feed passing first through said new bed Cthen through partially exhausted bed A, and recovering a sweetened,non-corrosive product from each of said contacting sequences.

9. A process as defined in claim 8 wherein said contacting beds A, B,and C are composed of a major proportion of an alkaline fullers earth,and a minor proportion of commercial litharge.

10. A method for sweetening a sour hydrocarbon feedstock to obtain anon-corrosive product therefrom, which comprises passing a stream ofsaid feedstock through a bed of clay and lead oxide to obtain aninitially corrosive product, periodically sampling the effluenttherefrom and determining its corrosivity, recycling the corrosive,sweetened product initially obtained and blending it with a largerquantity of untreated feedstock in storage until the efiluent becomesnon-corrosive, and then discontinuing the recycle of efiluent tofeedstock storage and collecting a sweetened non-corrosive product.

11. A continuous process for treating a sour, corrosive hydrocarbonfeedstock to obtain a sweetened product of reduced corrosivity whichcomprises providing two beds A and B of solid lead oxide-clay mixture,bed A being virgin and bed B being partially exhausted as a result ofprevious contacting with feedstock for a period of time such that theinitially corrosive efiiuent therefrom has become non-corrosive but isstill sweet, establishing a first contacting sequence wherein said feedis passed first through bed A and then through bed B, continuing saidfirst contacting sequence until the initially corrosive effluent frombed A becomes non-corrosive and bed A is partially exhausted as abovedefined, then establishing a second contacting sequence wherein saidfeed is passed first through bed B and then through bed A, continuingsaid second contacting sequence until the initially sweet effluent frombed B becomes sour and bed B is exhausted, establishing a thirdcontacting sequence wherein said feed is passed only through bed A, andduring said third contacting sequence replacing bed B with a new bed Cof lead oxide-clay mixture, reestablishing said first contactingsequence with the feed passing first through said new bed C, thenthrough partially exhausted bed A, and recovering a sweetenednon-corrosive product from each of said contacting sequences.

12. A process as defined in claim 11 wherein said hydrocarbon feedstockis a lower paraflin hydrocarbon.

13. A process as defined in claim 11 wherein said hydrocarbon feedstockis a light gasoline fraction. 1

14. A process as defined in claim 11 wherein said hy-; drocarbonfeedstock contains at least two gram-atoms of l mercaptan sulfur pergram-atom of corrosive sulfur.

15. A method for treating a sour, corrosive hydrocarbon stream to removeboth mercaptan sulfur and corrosive sulfur therefrom, which comprisesfirst pretreating a fresh bed of clay-lead oxide mixture with a sourhydrocarbon stream until the originally corrosive efiluent therefrom hasbecome non-corrosive, terminating said pretreatment before themercaptan-absorbing capacity of said bed has been depleted, thencontacting said sour, corrosive hydrocarbon stream with the pretreatedbed and recovering a sweet, non-corrosive product, and further treatingsaid originally corrosive effluent to remove corrosive sulfur.

16. A method for treating a sour, corrosive hydrocarbon stream to removeboth mercaptan sulfur and corrosive sulfur therefrom, which comprisesfirst pretreating a fresh bed of clay-lead oxide mixture with a sourhydrocarbon stream until the originally corrosive effluent there fromhas become non-corrosive, terminating said pretreatment before themercaptan-absorbing capacity of said bed has been depleted, thencontacting said sour, corrosive hydrocarbon stream with the pretreatedbed and recovering a sweet, non-corrosive product.

17. A method for treating a sour, corrosive hydrocarbon stream to removeboth mercaptan sulfur and corrosive sulfur therefrom, which comprisesfirst pretreating a fresh bed of clay-lead oxide mixture with a sourhydrocarbon to obtain an initially corrosive product, continuing saidpretreatment until the hydrocarbon product is non-corrosive, then,before the corrosive-sulfur removing capacity of said pretreated bed isexhausted, contacting said sour, corrosive hydrocarbon stream with a bedof clay-lead oxide including, at least at the downstream end thereof,said pretreated bed and recovering from said contacting a sweetnon-corrosive product.

References Cited in the file of this patent UNITED STATES PATENTSGilbert Feb. 13, 1945 i

1. IN A PROCESS FOR REMOVING CORROSIVE SULFUR AND MERCAPTAN SULFUR FROMA HYDROCARBON FEED CONTAINING THE SAME, WHEREIN SAID FEED IS TREATED INA CONTACTING COLUMN WITH A BED OF CLAY-LEAD OXIDE MIXTURE, THE IMPROVEDMETHOD OF OPERATING SAID PROCESS TO OBTAIN A REGENERATIVE OPERATIONPRODUCING A CONTINUOUSLY SWEET AND NONCORROSIVE PRODUCT, WHICH COMPRISES(1) FIRST PASSING SAID FEED THROUGH A FRESH BED OF CLAY-LEAD OXIDEMIXTURE UNTIL THE MERCAPTAN-REMOVING CAPACITY OF SAID BED ISSUBSTANTIALLY EXHAUSTED AND THEN TERMINATING THE PASSAGE OF FEEDTHERETHROUGH BEFORE THE CORROSIVE SULFUR-REMOVING CAPAC-